1. Field of the Invention
The present invention relates to a heat exchanger for use as an evaporator or a condenser for an air conditioner or for a radiator or heater core for vehicle or other type heat exchanger, and a method for manufacturing the heat exchanger.
2. Description of the Prior Art
FIGS. 6 and 7 show a typical conventional heat exchanger which allows heat to exchange between a heat exchange medium (for example, cooling medium or brine) flowing in the heat exchanger and air passing through the heat exchanger. A heat exchanger 21 shown in FIG. 6 comprises a serpentine flat tube 22 through which a heat medium passes, a plurality of radiation fins 23 provided on the sides of the substantially parallel portions of the tube, and unions 24 connected to the end portions of the tube.
Union 24 has a hexagonal outer shape in cross section and has a screw thread 24a on the surface of its one end portion, as shown in FIG. 7. In union 24, a flat insertion hole 24b is formed having substantially the same shape in cross section as tube 22 and into which the end portion of tube 22 is inserted, In addition, passage hole 24c, having a circular cross section, is also formed in union 24.
Radiation fins 23 are brazed on the sides of the parallel portions of tube 22. The end portions of tube 22 are inserted into the insertion holes 24b of the respective unions 24, and fixed to the respective unions at portions A by brazing.
The heat exchanger is manufactured usually by inserting each end portion of tube 22 into each union 24 after brazing radiation fins 23 and the tube in a furnace, and subsequently connecting and fixing the end portion of the tube to the union by brazing.
In such a conventional heat exchanger, however, since the connection of tube 22 and union 24 is performed in a separate operation from the brazing of tube 22 and radiation fins 23, the manufacturing process of the heat exchanger is complicated and expensive. Moreover, because tube 22 and union 24 are brazed manually by a worker, the quality of the brazing is difficult to control. The quality of the brazed portions obtained by such a manner varies according to the abilities of individual workers. Poorer quality brazed portions are likely to deteriorate. If the brazing is not performed in a desired manner, a crack is liable to occur in the brazed portion, and a fluid is likely to leak from the brazed portion.